Implantable heart pump

ABSTRACT

An implantable Starling-type heart pump which may be adapted for use as a total artificial heart, or as a single ventricle device replacing one side of the heart. A rigid case, mounting blood input and output valves, houses a variable displacement piston pump. A separate spool-type pump control valve assembly directs motive force from a power source which may be gas or other fluid pressure, electro-mechanical or heat energy conversion for alternately initiating piston retraction and extension upon receipt of a signal pulse from the piston pump itself. Blood chamber displacement is a function of pressure and available blood volume.

Umted States Patent [191 [1 1 3,9 Davis Nov. 4, 1975 [75] Inventor: PaulKnight Davis, Alemeda, Calif. Artificial lntracorporal Heart, by F, W.Hastings et 73 Assignee; P ifi Roller Die Co Inc" al., TransactionsA.S.A.I.O., Vol. 7, 1961, pp.

Hayward, Calif. A Servomechanism to Drive an Artificial Heart In- [22]Flled' 1974 side the Chest, by K. W. Hiller et a1., Transactions, 2 APPL525 31 A.S.A.I.O., Vol. 8, 1962, pp. 125-130.

Related Application Data Primary ExaminerRonald L. Frinks [63]Continuation of Ser. No. 312,668, Dec. 6, 1972,

abandoned. 57 TRAC An implantable Starling-type heart pump which may[52] U.S. Cl. 3/l.7, 128/205 Rial/733,95, be adapted for use as a totalartificial heart or as a [5]] Int Cl 2 A61F 1/24 single ventricle devicereplacing one side of the heart. [58] Fieid S D DIG 3 A rigid case,mounting blood input and output valves, /21 M7689 3 houses a variabledisplacement piston pump. A separate spool-type pump control valveassembly directs References Cited motive force from a power source whichmay be gas or other fluid pressure, electro-mechanical or heat en-UNITED STATES PATENTS ergy conversion for alternately initiating pistonretrac- 3,182,335 5/1965 Bolie 3/ 1.7 tion and extension upon receipt ofa signal pulse from ,6 1970 y the piston pump itself. Blood chamberdisplacement is 3,568,214 3/1971 Gddschmled a function of pressure andavailable blood volume. 3,633,217 l/l972 Lance 3,783,453 1/1974 Bolie3/1 7 18 Claims, 24 Drawin Figures 120 76 22 -4 I 75 77 34 88 l 9 35 8,V 86 23 "H Z5 7 I I 6 30 4 H l i & a 4737 '5 85 i 50 5s 53:-5 1 i l :63I 101- 7 39- 5Z ii i s A 67 t a 60 j US. Patent NOV.4, 1975 Sheet 1 of15 3,916,449

U.S, Patent Nov. 4, 1975 Sheet20f 15 3,916,449

US Patent Nov. 4, 1975 Sheet3of 15 3,916,449

II I FIE:- -F5- US. Patent Nov.4, 1975 Sheet50f 15 3,916,449

Sheet 6 of 15 US. Patent Nov. 4, 1975 U.S. Patent Nov. 4, 1975 Sheet 7of 15 3,916,449

US. Patent Nov. 4, 1975 Sheet8of 15 3,916,449

US. Patent Nov. 4, 1975 Sheet 9 of 15 w 185 183 6 W J o a FIG- .13.

U.S. Patent NOV.4, 1975 Sheet 10 of 15 3,916,449

FIE- -14- U.S. Patent Nov.4, 1975 Sheet110f15 3,916,449

U.S. Patent Nov. 4, 1975 Sheet 12 0f15 3,916,449

U.S. Patent Nov. 4, 1975 Sheet 13 of 15 3,916,449

U.S. Patent Nov.4, 1975 Sheet 14 0f 15 3,916,449

FIE--ZCI- FIG- .15].

60 5TKOKE5 PER MIN. """"IZO STRUKES PER MIN.

U.S. Patent NOV.4, 1975 Sheet 15 of 15 3,916,449

IMPLANTABLE HEART PUMP This is a continuation of application Ser. No.312,668, filed Dec. 6, 1972 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to prostheticdevices, and more particularly to a Starling-type heart pump which inalternate forms is utilizable either as a total natural heartreplacement or an assist device in conjunction with the natural heart.

Hertofore, various forms of artificial blood pumps have been developedfalling into either heart assist device or total artificial heartcategories. Heart assist de vices have been developed for supplementingthe pumping action of either the left or right ventricles of the heart.However, the left ventricle is more subject to failure, since it ejectsblood to the aorta, works against the resistance of the wholecirculatory tree and performs several times the work or pumping actionof the right ventricle emptying into the less resistant pulmonary sytem.

One of the known heart assist devices is designed to operate in parallelwith the left ventricle through connection between the left atrium andthe descending aorta, and comprises a rigid tubular housing within whichis a flexible tube or bladder having valves at each end. Air pulsesintroduced between the rigid and flexible tubes intermittently contractand expand the flexible tube for pumping blood within the inner tube. Avariation of this in parallel assist device utilizes adiaphragm-operated pumping chamber actuated by air pulses for pumpingblood from the left ventricle to the aorta. Another existing form of airpulse driven in parallel assist unit is designed to be connected betweenthe apex of the left ventricle and the descending aorta. US. Pat. No.3,550,162, to Hoffman et al. discloses a form of assist device of thegeneral type discussed.

A known form of in-series assist device is connected between theascending and descending parts of the aorta, with the ascending aortainterrupted between the points of connection. In similar fashion to theparallel type devices, it is operated by air pulses and pumps bloodwithin an intermittently expanded and contracted flexible tube. All suchassist devices are capable of performing only a part of the workload ofthe defective side of the heart, will stall in the absence ofappreciable blood volume and pressure in the left heart chamber andtherefore are incapable of serving as a temporary or permanentreplacement for the left or SUMMARY OF THE INVENTION The two principalcomponents of the heart pump of this invention are a variabledisplacement piston-type 5 blood pumping unit, which in a preferredembodiment right side of the heart when it is rendered incapable ofperforming a filling or ejecting function. .The devices all suffercommon problems of objectionable blood damage, clotting and diaphragmfailure.

Total artificial hearts which have been proposed have incorporated bothtwo and four chambers, corresponding to the ventricles and atria of theheart. These total heats have incorporated diaphragm pumps which may beactuated by air or compressed carbon dioxide pulses. One fonn of totalheart utilizes oil as a pumping fluid to compress a sac for forcing theblood into the aorta. Problems of blood flow interference, clotting andblood damage are aggravated in total artificial hearts because of thegreater number of valves, chambers, material interfaces and passagestherein, resulting in greater contact with and abuse of the blood.

is air-driven, and a spool-type control assembly therefor. The pumpingunit is adapted for implantation. The control assembly is external andutilizes an air supply, connections and manual emergency control means.The complete heart pump requires, in addition to the two maincomponents, only a source of compressed air and suitable air lines, thusall equipment is readily borne by the user and is transportable.

The pumping unit has a rigid case providing either one or two majorblood chambers corresponding to the ventricles of the heart, dependingon whether the unit is to replace one or both sides of the naturalheart, and each major blood chamber has an associated blood intake valveand a blood outlet valve. A variable displacement blood piston ismounted for reciprocation within each blood chamber for alternatelycausing blood to be expelled through the outlet valve (systole) and tobe received through the inlet valve (diastole). In the form of pumpingunit having two major blood chambers initiation of systole or diastoleoccurs simultaneously in both chambers as in the case of the naturalheart. A significant feature of the pumping unit is the inherentsensitivity of the blood pistons to venous pressure and blood volume. Asdistinguished from prior artificial heart pumps, little or no venouspressure is required for blood chamber filling. Displacement of theblool piston is also affected by displacement of a pressured air drivendouble acting cylinder that impels the blood piston during systole.

The control assembly is a signal controlled spool-type valving assemblyhaving only two moving parts, which are two spools respectively termed amain spool or main directional spool arid a signal directional spool orreversing spool. The two spools and associated ports and passagescontrol two distinct air circuits, one of which is the working aircircuit controlled by the main spool for transmitting-air to drive areciprocating air cylinder within the pumpingunit and the associatedblood piston. In a preferredforrn of control assembly, working pressuresare separately regulated during the systolic and diastolic phases, whichaffects the working rate of the blood piston during its systolic anddiastolic functions. In this way the complete pumping cycle may be madeto closely approximate the pressure-time signature of the human heart.Working pressure associated with each individual blood chamber of a twochamber pumping unit may also be separately regulated. The otherassociated circuit is an air pulse signal circuit.

The pumping unit is so constructed that at the points of completeextension or retraction of the air cylinder(s) in the single or doublechamber pumping units, an air pulse or signal circuit is opened withinthe pumping unit, and a pulse of air is returned from the pumping unitthrough the corectly positioned signal directional spool of the controlassembly and directed to a portion of the main spool for displacing ittothe position at which it will direct working air to the air cylinderor cylinders in the pumping unit for causing reverse displacementthereof. The rate of reciprocation of the control spools corresponds tothat of the blood pistons and is the heart beat rate. The controlassembly is therefore a passive or slave device relative to the pumpingunit in that the air pulse or signal depends only upon positioning ofelements of the pumping unit itself which, in turn, are sensitive toblood pressure and volume values that control the filling and thereforethe ejection volume. A multiple channel conduit is connected between thepumping unit and control assembly for providing the necessary workingair, pulse signal air and case venting lines, and conductors for heartfunction monitoring devices when desired. I

A preferred form of heart pump of this invention includes novel intakeand outlet valves, both of which are of a flexible, tricuspid designcharacterized by extremely low pressure requirements for opening andclosing, smooth operation and absence of regurgitation. Mounting of thevalves in close proximity to each other is also important in order tosustain adequate flow in the blood chamber. r

The air circuitry in this heart pump provides a sort or cushionedtransition at reversal of blood piston displacement. The arrangement ofthe blood piston within a chamber is such that the circulation of bloodwithin a blood chamber follows a generally circular path from inletvalve to outlet valve. The blood piston is main tained in a sealingrelationship with the case of the pumping unit defining theblood-chamber by a novel sealing ring which hasa cross-sectionalconfiguration yielding a rolling action which precludes entrapment ofblood between the. sealing ring and surfaces of the blood chamber andblood piston which it contacts. The overall result is reduction of bloodstagnation and turbulence and blood abuse. i V

Important objects of the invention are provision of a highly reliable,implantable, Starling-type. heart pump suitable as an assist device forone side of the heart or as a total artificial, heart; and artificialheart pump which lessens damage to the pumped blood relative to thatcaused by prior devices; a heart .pump that will continue to cycle uponloss of filling volume as a result of heart-.disfunction, but will ceasefunctioning in the event of excessive arterial blockage; and a heartpump and pump system that are readily borne and trans ported by the userand require no auxiliary equipment.

Further objects are to provide an aritificial heart pump in which,relative durations of the systolic andiastolic phases and bloodpressures within the pump during such phases closely. approximate thecorresponding characteristics of the natural heart; a heart pump havinga simple beat rate control; a heart pump incorporating means foraccurately monitoring blood output; and a heart pump which can readilybe. manually controlled in the event of automatic control functionfailure.

Additional objects are to provide in a heart pump combination, a pumpingunit control having substantially fewer operating parts than heretofore;novel heart valves which operate in a manner less abusive of blood thanprior prosthetic valves; and a novel blood sealing ring exhibiting arolling action which precludes entrapment of blood.

Other objects and advantages of the invention will become apparaent fromthe following description of preferred embodiments of the invention.

DESCRIPTION OF THE FIGURES porating a double-chamber pumping unit,showing its.

connection with an air source and with associated portions of the bloodcirculation system;

FIG. 2 is an end elevational view of the pumping unit of FIG. 1, withparts broken away;

FIG. 3 is an enlarged vertical cross-sectional view of the pumping unitshown in FIG. 1, taken substantially along line 3-3 thereof; I

FIG. 4 is an enlarged vertical cross-sectional view of the pumping unitof FIG. 1, taken along a plane disposed from theplane of FIG. 3 andalong line 4-4 in FIG. 3.

FIG. 5 is an enlarged horizontal cross-sectional view of the pumpingunit of FIG. 1 showing the blood pistons thereof in the fully retractedposition;

FIG. 6 is an exploded fragmentary view showing a portion of the bloodpiston sealing ring in the pumping unit of FIG. 1, with associatedparts;

FIG. 7 is a fragmentary cross-sectional view of the air cylinders andassociated parts of the pumping unit of FIG. 1;

FIG. 8 is a fragmentary view of a signal jet tube assembly in the'airsignal circuit of the heart pump of FIG. .1;

FIG. 9 is a partially cross-sectional, partially schematic view showingthe pumping unit of FIG. 1 and a form of control assembly therefor, withthe parts positioned at the completion of the filling or diastolic phaseof the pumping cycle;

FIG. 10 is a view similar to FIG. 9, but. showing the positions of partsat completion of the blood ejection or systolic phase of the pumpingcycle;

FIGS. 1 1a and 1 1b are partial cross-sectional views of the pumpingunit of FIG. 1 during the diastole phase, taken along the sameplane asFIG. 10, showing two stall conditions; 1

FIG. 12 is a partially cross-sectional, partially schematic view of thepumping unit of FIG. 1 with a moodified form of dual pressure controlassembly;

FIG; 13 is an exploded view of control assembly componentsand associatedparts of the heart pump of FIG.

FIG. 14 is an isometric view of the air circuitry in the controlassembly of FIG. 1;

FIG. 15 is an enlarged top plan view, with parts broken away, of thecontrol assembly of FIG. 1;

FIG. 16 is an end view, with parts broken away, of the control assemblyshown in FIG. 15;

FIG. 17 is a partially cross-sectional, partially schematic view of aform of single-chamber pumping unit and control assembly therefor,showing the positions of parts at the end of the diastolic phase;

FIG. 18 is similar to FIG. 17, but shows the positions of parts at theend of the systolic phase;

FIG. 19 is a fragmentary view of a preferred form of inlet valve for thepumping unit of FIG. 1;

FIG. 20 is a fragmentary view of a preferred form of outlet valve forthe pumping unit of FIG. 1;

FIG. 21 is a graph showing the relationship between venous pressure andblood filling volume exhibited by the pumping unit of this invention,when operating at 60 and beats per minute;

FIG. 22 is a fragmentary view of a modified form of blood piston sealingring; and

FIG. 23 is aschematic view of a modified form of control assemblyutilizing three different operating pressures and associated parts of adouble-chamber pumping unit of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Double-Chamber Pumping Unit vPumping unit 11 (FIGS. 1 and 3) comprises a rigid case formed of a pairof similar, generally hemispherical, rigid case members 17 and 18, eachhaving squaretoothed annular edge portions 19 and 22 respectively whichare in interfitting relation. Each case member also has formed thereintwo parallel open-ended tubular protrusions 23, 24, 25 and 26 providingtwo ports for each case member. The case is preferably fabricated froman inert plastic material, such as polycarbonate plastic, which will besuitable for implantation and will withstand autoclave sterilization.

FIG. 1 schematically illustrates portions of the human circulatorysystem directly communicating with the valves of the heart,specifically, the veina cava 27, pulmonary artery 28, lungs 29,pulmonary veins 32 and aorta 33. Tubular ports 24 and 26 respectivelyare provided for surgical connection with the pulmonary artery 28 andthe ascending portion of the aorta 33. Ports 23 and 25 respectively areadapted for surgical connection with the natural right atrium associatedwith the vena cava 27 and the natural left atrium associated with thepulmonary veins 32, for introduction or ejection of blood through valvesto be described.

A circular plate member 30 (FIGS. 3 and 4), which may also be formed ofan inert plastic material, is located within the pump case with itsperiphery in contact with the interior surface'of edge portions 19 and22. Member 30 has a peripheral flange portion 34 and is secured to caseedge portion 19 (FIGS. 4 and 5) and 22 (FIGS. 3 and 5) by a series ofscrews 35. The central portion of member 30 has a cylindrical shapeprojecting in both directions axially of member 30 i (FIGS. 3 and 7)which provides a stationary cylinder rod 36 of a double acting cylinderassembly. Respectively fixed to the ends of rod 36 in case members 17and 1.8 by screws 39 are circular pistons 42 and 43, and a central bore38 extends fully through pistons 42 and 43 and rod 36. An O-ring 60 isseated around the periphery of each piston 42 and 43.

Slidingly received within bore 38 is a rod 52 (FIGS. 3

and 7) that is slightly shorter than rod 36. Rod 52 has a central bore53 extending from its end within case member 17 but terminating short ofits opposite end. A second rod 54 is received within the bore 53, and atthe outer end of rod 52 there is fixed, by a screw 57, the flat face 50of an air cylinder 55 having its cylindrical wall 51 seated aroundO-ring on piston 42. The open end of cylinder 55 is threaded around theperiphery of a ring 46 which is slidingly fitted around rod 36 insealing relation thereto by an O-ring 48. When cylinder face 50 is incontact with piston 42, ring 46 contacts a shoulder 56 of plate member30. Cylinder 55 with ring 46 slides relative to rod 36 and piston 42 andcarries rod 52 with it. Rod 54, received within bore 53 of rod 52 hasfixed to it by a screw 63 a flat faced air cylinder 59 having acylindrical wall 61, threaded around a ring 47. Rod 54 with cylinder 59thereon, slides within rod 52 relative to rod-36 nd piston43. O-rings 60and 48are respectively seated: in piston 43 and ring 47.

The inner surface of case member 17 immediately adjacent edge portion 19(FIG. 6) is formed with a stepped section providing a threaded portion64 and a flat portion 65 terminating in a rectangular groove 66. Thissection of case member 17 provides seating for elements of an assemblyfor mounting a hollow piston 67 (FIGS. 2,3 and 6), which overlies aircylinder 55, and as will be described, reciprocates for pumping bloodpresent in the chamber defined between the piston and case wall. Theleading end of piston 67 is partially tapered forwardly to a flat face(FIG. 3). The interior defines a cylindrical chamber 81 (FIG. 6) havingan annular shoulder 82 inside its face 80. When cylinder 55 (FIG. 3) iswithin piston 67 with face 50 contacting shoulder 82 of the piston,there is clearance space between the opposed surfaces of the piston andair cylinder for purposes to be described.

The annular open end of piston 67 is formed with an annular groove 68(FIG. 6) of L-shaped cross-section, and piston 67 is sealingly attachedto case member 17 by a resilient sealing ring, which may be formed ofsilicone rubber material, and which, when in an uncompressed conditionhas a cross-section as shown in FIG. 6, including a T-shaped portion 72,a C-shaped portion 73 and a pair of opposed L-shaped portions 74.,Ring.69 is attached to case member 17 (FIGS. 3 and 7) by the T-shapedportion 72 inserted in slot 66 and is retained therein by a retainingring 75 received within the case portion 65 and having a notched end formating with the portion 72. An annular retaining-nut 76 is threaded intothe threaded case portion 65, and resilient sealing ring 77 iscompressed between nut 76' and flange portion 34 of plate member 30.

On the piston 67 itself, one of. the I -shaped portions 74 of sealingring 69 is seated within the L-shaped groove 68 and the other portion 74is compressed thereagainst by a retaining ring 78 having an L-shapedgroove 79. Retaining ring 78 is screwed to piston 67 by a series ofscrews 90. It is seen (FIGS. 3 and 6) that with the described assembly,portion 73 of sealing ring 69 will effect a rolling motion relativetothe cylindrical surface 83 of piston 67 and the opposed surfaces ofcase member 17, ring 75 and nut 76, during reciprocation of piston 67,and such rolling action precludes entrapment of blood between suchsurfaces. A piston 85, (FIG. 3) similar to and mounted in the samefashion as piston 67 faces the opposite direction therefrom within casemember 18. Mounting means for piston 85 includes sealing ring 86,retaining ring 87, retaining nut 88, sealing ring 89 and retaining ring92.

A blood chamber (FIG. 3) is defined between blood piston 67 and casemember 17, and a similar blood chamber 101 is associated with piston 85.The chamber surfaces are treated with Dacron fibers to support andretain live fetal cells or natural tissue growth. Blood is drawn intochambers 100, 101 upon retraction of pistons 67 and 85, and expelledupon extension of the pistons. Port tube 23, associated with piston 67,and port tube 25, associated with piston 85, are respectively providedfor surgical connection with the right atrium associated with veina cava27 (FIG. I) and the left atrium associated with pulmonary veins 32 andfor mounting'blood inlet valves. preferred form of inlet valve (FIG. 19)utilized to replace the tricuspid and'rnitral valves of the naturalheart, is a flexible, normally open three-leafed valve, which may bemolded of a silicone rubber material. Valve 120 includes a collarportion 121 for seating and vulvanizing into the outer end of a porttube 23, 25 (FIG. 3). Integral with the collar portion 121 are threesimilar leaves 130 (FIG. 19) each molded along a generally semicircularline of attachment with the collar portion,'opening in the direc tion offlow into the pumping unit and spanning onethird the distance aroundcollar portion 121. The leaf inner end 140 can best be described asresembling in shape the pointed bottom end of a shield. A dart shapedreinforcing portion 141 is molded onto the inner face of leaf 130 at thecenter point of inner end 140 thereof. Relative to the interior of thevalve, leaf 130 is mildly convex adjacent its line of attachment tocollar portion 121 and mildly concave adjacent dart shaped portion 141.In the normally open condition inner ends 140 of the three leavestogether define an inwardly opening triangular mouth. The mouth isenlarged by flexing of leaves 130 during introduction of blood to thepumping unit (diastole) and is closed to flow of blood during expulsion(systole). Dart shaped portions 141 contribute to effective closure andsealing of leaves 130 during systole.

Each outlet valve 170 (FIG. 20) used is a threeleafed normally closedvalve, which includes a collar portion 171 for seating in port tubes 24and 26. Three similar leaves 180 are molded to collar portion 171 alonga generally semicircular line of attachment spanning one third thedistance around collar portion 171 and opening away from pumping unit 11so that the leaves open outwardly thereof. Relative to the interior ofthe valve the leaves are convex, and the outer end portion 181 of eachleaf (FIG. 20) includes two straight equal legs defining a 120 angle. Inthe closed condition, as during diastole, the end portions 181 of leaves180 are in sealing contact to prevent reverse flow of blood. Duringsystole or outflow the flexible leaves separate to provide athree-pointed outward opening mouth for passage 'of blood. Also, duringoutflow, the leaves exhibit an outwardly directed bulging effect whichis of importance as the leaves thus impel blood which otherwise mightundesirably remain at the outer surfaces of the valves.

Cylinder 55, with ring 46 and cylinder 59 with ring 47 reciprocate inopposite directions relative to rod 36 as double-acting cylinders, andtheir reciprocation is synchronized so that both simultaneously initiatean extension or retraction stroke. Appropriate passages and porting forsynchronization include through bore 93 (FIG. 7) extending through rod36 and pistons 42 and 43 in parallel with bore 38. Another passage 94extends in parallel on the opposite side of bore 38, but is closed atboth ends and communicates with a passage 99 leading to an area betweenpiston 42 and ring 46, and also with a passage 102 leading to an areabetween piston 43 and ring 47. FIGS. 3, and 7 show cylinders 55 and 59and spools or rods 52 and 54, in the completely retracted position.Inner spool 54 includes a reduced diameter portion 95 (FIG. 7) locatedto span the midpoint of bore 38 when spool 54 is retracted. Outer spool52 includes a series of three reduced diameter portions 96, 97 and 98.When spools 52 and 54 are retracted, portion 96 is at the midpoint ofbore 38, portion 97 is spaced toward cylinder 59 but overlies portion 95of inner spool 54, and portion 98 is midway between portion 97 and thefree end of the spool. A passage 103 extends between passage 94 and bore38 in 8 rod 36 and communicates with spool portion 97 when rod 52 isretracted. A passage 104 extends between bores 38 and 93.

Blood output from a blood chamber 100, 101 is readily and accuratelymeasured by utilizing a small bar magnet 283 (FIG. 9) embedded withinthe associated blood piston 67, with an end flush with the piston inneredge surface, and a sensor 284 mounted in alignment therewith on theopposed surface of central plate member 30. Sensor 284 is a Hallmagnetic effect transducer which provides a varying electrical outputwhen subjected to a varying magnetic field. The amplitude of variationin electrical output is a direct function of the variation in strengthof the magnetic field. As has been described, the output of the pumpingunit depends on blood piston dislacement, and correspondingly, theamplitude of the change in electrical output from the transducer dependson the distance between its blood piston and stationary central platemember 30. An electrical connection 285 within an additional channel ofconduit 13 is provided between transducer 284 and an external electricalrecording device of conventional construction. For example, thetransducer can be connected to an oscillograph which will record a plotof the electrical output variation during travel of the blood piston,i.e., a plot of blood piston displacement. Such plot readily iscalibrated and translated so that blood output volume per stroke candirectly be represented on the oscillograph graphs.

As seen in FIGS. 1 and 13 conduit 13 for introducing pressured air topumping unit 11 is a flexible ribbon having multiple air channels.Conduit 13 is preferably formed of extruded silicone rubber and at theend which connects with pumping unit 11 receives multiple rigid tubes105, 106 and 108, and T-tubes 107 and 113 (FIGS. 4 and 13) whichcommunicate with the interior of the pumping unit. Conduit 13 extendsthrough the case, through flange portion 34 of plate member 30 and anopening 109 therein. The rigid tubes are clamped in the end of conduit13 by a pair of clamp plates (FIGS. 4 and 3) within the opening 109.Tubes 105, 106 and 108 respectively communicate with passage 93, bore 38and passage 94, and T-tubes 107 and 113 terminate within clamps 115 andcommunicate with opening 109. The opposite end of conduit 13 is adaptedto be connected to a control assembly for pumping unit 11 such ascontrol assembly 12 (FIGS. 1, 13, 15, 16), the main component of whichis a spool valve assembly, e.g., 117 (FIGS. 1, 9, 10 and 14), 201 (FIG.12) or 230 (FIG. 23).

Control Assembly A preferred form of control assembly 12 incorporatingspool valve assembly 117 (FIGS. 1, 9, 10 and 14) has an associatedhousing 160 (FIGS. 1 and 16) for an air pressure gage 174 (FIG. 16).Valve assembly 117 (FIGS. 13 and 15) includes a valve body 119 forseating a main spool 122 having a circular piston 123 on one end and asimilar piston 124 on the opposite end, and for seating a reversingspool 125 having a single piston 126 at one end. A port plate 127 ismounted on the top surface of valve body 199, a cap 128 is at the sideadjacent to piston 123 of main spool 122 and a cap 129 is at theopposite side.

The control end of conduit 13 receives rigid tubes 105a, 106a, 107a,108a and 113a (FIG. 13) respectively in the same channels as tubes 105,106, 107, 108

. and 113. Each such tube communicates with a port in

1. A heart pump, comprising: a. a housing; b. a blood pumping elementmounted in said housing for opposed systolic and diastolic displacementrelative to a portion of said housing and defining with said portion ablood chamber; c. inlet means and outlet means communicating with saidchamber; d. drive means in said housing having an independent,predetermined driving period; e. means substantially associating saiddrive means with said pumping element during said period for effectingsystolic displacement of said element; and f. said drive means beingsubstantially disassociated from said pumping element during diastolicdisplacement, whereby diastolic displacement of said element issubstantially directly related to blood pressure and volume presented atsaid inlet means.
 2. The heart pump of claim 1 in which: g. a pair ofsaid blood pumping elements and a pair of portions of said housingdefine a pair of blood chambers; h. a pair of said drive means, eachassociated with one of said elements, having the same driving period. 2.a main spool means seated within said valve body for displacement underurging of said gas for controlling passage of said gas through saidpassages to said main spool means for initiating displacement thereof;3. The heart pump of claim 1, including: g. means yieldably urging saidelement in the direction of diastolic displacement.
 4. The heart pump ofclaim 1, in which: g. said driving perioD includes extension andretraction; and h. means temporarily associating said drive means withsaid element during the initial portion of retraction for initiatingdiastolic displacement of said element.
 4. said cylinder and saidcontrol assembly being operably connected such that passage of said gasfrom said reversing spool to said main spool is responsive todisplacement of said cylinder.
 5. The heart pump of claim 1, including:g. means temporarily cushioning the association of said drive means withsaid element during the initial portion of said driving period.
 6. Animplantable heart pump, comprising: a. means defining at least one bloodchamber; b. blood inlet means for each said chamber; c. blood outletmeans for each said chamber; d. a housing for pump components; e. eachsaid blood chamber partially defined by an associated portion of saidhousing; f. a blood pumping element associated with each said chamberand defining a portion thereof; g. each said pumping element beingadapted for variable reciprocating displacement relative to saidassociated portion of said housing along a path of displacement; h. eachsaid pumping element including within said housing venous blood responsemeans for directly relating said displacement to blood pressure andvolume presented at said blood inlet means associated therewith wherebythe volume of blood filling of said chamber inherently is responsive tothe blood volume and pressure so presented; i. sealing means associatedwith each said blood chamber between said portion of said housing andsaid pumping element; j. said pumping element having a wall with a firstsurface for contacting blood in said blood chamber and an oppositesecond surface sealed from said first surface by said sealing means; k.cylinder means adapted for reciprocating displacement along said pathand having a surface in opposed relation to said second surface of saidwall; l. drive means for imparting said reciprocating displacement tosaid cylinder means; m. said pumping element and said cylinder meansbeing operably connected such that they are displaceable relative toeach other and also are adapted for displacement together.
 7. Theimplantable heart pump of claim 6, wherein: n. said drive means for saidcylinder means is responsive to displacement of said cylinder means. 8.The implantable heart pump of claim 7, wherein: o. said drive means is agas actuated means.
 9. An implantable heart pump, comprising: a. ahousing; b. a blood chamber partially defined by a portion of saidhousing; c. a blood inlet for said chamber; d. a blood outlet for saidchamber; e. a blood pumping piston defining a portion of said chamberand being adapted for reciprocating variable displacement relative tosaid portion of said housing along a path of displacement; f. resilientsealing means between said portion of said housing and said piston; g.means in said housing for rendering the displacement of said pistonrelative to said portion of said housing dependent on the volume andpressure of blood presented at said blood inlet means for filling ofsaid chamber; h. said piston having a hollow portion opening away fromsaid chamber in the direction of said path of displacement; i. a doubleacting gas cylinder located within said hollow portion and displaceablealong said path for initiating said displacement of said piston; j. asource of gas under pressure; k. a gas conduit between said source andportions of said gas cylinder; l. a gas control assembly interposedbetween said gas cylinder and said gas source for directing said gas todifferent portions of said gas cylinder for alternately initiatingforward and reverse displacement of said gas cylinder; m. said cylinderand said control assembly being operatively connected such that theinitiation of displacement of said gas cylinder is responsive topositioning of said gas cylinder along said path.
 10. The implantableheart pump of claim 9, including: n. a stationary rod extending axiallywithin said cylinder and having gas passages therein; o. a central borein said stationary rod; p. a central rod within said bore and fixed tosaid cylinder for displacement therewith and having gas passagestherein; q. said passages in said stationary rod and in said central rodbeing alignable according to said positioning of said cylinder forpassage of gas from said source for initiation of said displacement ofsaid cylinder.
 11. The implantable heart pump of claim 9, wherein: n.said piston and said cylinder have opposed surfaces with clearance spacetherebetween; and o. said clearance space is in communication withatmospheric air.
 12. The implantable heart pump of claim 9, wherein: n.said gas control assembly includes:
 13. The implantable heart pump ofclaim 9, wherein:
 14. An implantable heart pump, comprising: a. a rigidpump case; b. a variable displacement blood piston in said case; c.means for displacing said blood piston; d. a blood inlet valve and ablood outlet valve mounted in said case respectively for passage ofblood thereinto upon retraction of said piston and therefrom uponextension of said piston; e. a control assembly for alternatelyinitiating extension and retraction of said piston; f. means forgenerating a signal within said case; g. said control assemblyinitiating said displacement of said piston responsive to transmissionof said signal from within said case; h. the distance of displacement ofsaid piston being dependent upon the volume and pressure of bloodpresented at said blood inlet valve; and i. movable means at theproximal side of said piston for displacement in the direction ofdisplacement of said piston and relative thereto, said transmission ofsaid signal to said control assembly being dependent upon the positionof said movable means.
 15. In an implantable heart pump including atleast one variable displacement blood pumping piston and a gas drivenmeans for alternately initiating systolic and diastolic displacement ofsaid piston, gas control means, comprising: a. a first circuit for gasfor driving said gas driven means; b. a second circuit for conductinggas pulses transmitted from said gas driven means when said means is inpositions for initiating said systolic and diastolic displacement ofsaid piston; c. a displaceable main spool interposed in said first andsecond circuits for directing driving gas to said gas driven means; d. adisplaceable reversing spool interposed in said first and secondcircuits for alternately directing said pulses to opposite ends of saidmain spool for causing reciprocation of same whereby driving gas isalternately directed by said main spool to different portions of saidgas driven means for alternately initiating said systolic and diastolicdisplacement of said piston.
 16. The control means of claim 15,including: e. pressure regulating means for regulating gas pressure insaid first circuit such that the pressure of gas applied to said gasdriven means during systolic displacement of said piston is higher thanthe pressure of gas applied during diastolic displacement.
 17. Thecontrol means of claim 15, including: e. adjustable nozzle means in saidsecond circuit for adjusting the duration and pressure of said gaspulses.
 18. The control means of claim 15, for use in said implantableheart pump having two Variable displacement blood pumping pistons andassociated gas driven means, including: e. a first portion of said firstcircuit for gas for driving one of said gas driven means; f. a secondportion of said first circuit for gas for driving the other one of saidgas driven means; g. pressure regulating means in said first circuit forseparately regulating the pressures of gas in said first and secondportions whereby different pressures are applied to each of said gasdriven means during systolic displacement of said pistons.